Answer:

These symbols are defined in the library and startup routine.
Check that the library (for example cI0.lib) is linked in order to use functions offered as a library.
Files such as described in section "2.2.2 Library files" in the CC78K0 User's Manual --Operation-- are provided.

Also, Check that the startup routine (for example, s0r.rel) linked.
The startup routine defines the processing, symbols, etc., required for starting up a C program.
As long as no substitute program is created, the startup routine needs to be linked.